1. Field of the Invention
The present invention relates to a registration board capable of dissipating static electricity through a conductive sink. The registration board is used in a vacuum frame exposure printing system that exposes a plate or film through the image of the desired copy material that has been placed inside the frame.
2. Background Art
When creating successive images of desired copy material (hereinafter "Copy"), each image in exact register with the registration system, multiple images are created by sequentially exposing light sensitive material through negatives or positives on top of the blanket in a conventional vacuum frame exposure system. It is necessary that the Copy maintain exact alignment through the multiple exposures. In so doing, it is possible to achieve dot-for-dot registration and a perfect reproduction of every line and dot over the entire image.
The prior art recognizes the use of a copy board and registration pins to maintain registration of Copy during an exposure process. For example, the patent to Carlson, U.S. Pat. No. 3,400,630, issued Sept. 10, 1968, shows alignment pins positioned on a copyboard insert set up to create an image on a frame of film. The positioning of material to be photographed is achieved by placing holes in the material over the alignment pins to establish a defined relationship with prepunched film positioned over fixed pins in the back of the camera. Continuity of register control is realized by projecting the image from the prepunched film to prepunched photographic plates where both the film and plates are pinned.
A vacuum frame exposure system has, however, two special problems that are not dealt with by the prior art.
First, because of the uneven movement of the blanket as a vacuum is created in the frame, there is the potential for movement of the plate or film being exposed in relationship to the vehicle holding the Copy resulting in what is commonly known as "tail-whip". As the glass cover of the vacuum frame is closed, the registration pins must descend vertically so that they are flush with the surface of the Copy. Even a small lateral movement of the pins as they descend will disrupt the register and the further the Copy is from the holes and pins, the greater the loss of register. Second, static electricity is generated before the glass cover is closed as the materials are moved in contact with each other. Because of the inability of the vehicle with the Copy and the Copy to move freely due to static electricity, the buildup of static electricity also results in a loss of register.
Loss of register in the vacuum frame is a consistent and costly problem. Loss of register in the vacuum frame is the single greatest source of loss of register in the graphic arts industry. Thus, a device which will increase the control of register and lessen the detrimental effects of static electricity would be greatly welcomed.